Electrical switch structures



1959 10. MOORHEAD ETAL 2,907,851

ELECTRICAL SWITCH. STRUCTURES Filed May 21, 1958 2 Sheets-Sheet 1 72lnventanis':

John 0. floorkeaai, Ra mand flfiulry,

0d. 6, 1959 Q, MOQRHEAD ETA k 2,907,851

ELECTRICAL SWITCH STRUCTURES Filed May 21, 1958 2 Sheets-Sheet 2Inventors: rfoizn 0.Moorizead, Raymond D. Mulrzy,

United States Patent 2,907,851 ELECTRICAL SWITCH STRUCTURES John 0.Moorhead and Raymond D. Mulry, Lexington, -Ky., assignors to TexasInstruments, Incorporated,

Dallas, Tex., a corporation of Delaware Application May 21, 1958, SerialNo. 736,833 14 Claims. (Cl. 200-138) This invention relates toelectrical switch structures and, more particularly, to such switchstructures which arethermally responsive.

Thermostatic or thermally responsive electrical switches, for one reasonor another, are often required to be provided in the form of a hollowcasing enclosing a thermal sensing element. For example, the interior ofthermostatic switches for refrigerators in many cases must be sealed offfrom the circumambient atmosphere to prevent the entry of moisture-ladenair thereby avoiding condensation on the internal parts of the switchand any resulting low electrical resistance path to ground along thesurfaces of these parts and/ or corrosive action on these surfaces. Theproblem arises in such cases and in others of providing for theeflicient transfer of heat between the temperature-sensing elementwithin the switch casing and the article whose temperature is to besensed.

'Another difiiculty frequently encountered in the art of thermallyresponsive switches is that of providing for the efficient transfer ofheat between an article: whose temperature is to be sensed and athermally responsive element of, for example, the type formed fromcomposite sheet material including layers having relatively differentcoefficients of thermal expansion; this particularly where therespective shapes of said element and said article are not compatiblewith each other so as to permit a substantial area of mutual contacttherebetween.

.An object of this invention is to provide a novel thermally responsiveswitch structure which overcomes the above and other difiiculties.

1 Another object of this invention is to provide a new and improvedswitch structure of the class described which exhibits improvedtemperature-response characteristics.

A further object of this invention is to provide such a novel switchstructure which is adapted for simple and reliable mounting on anarticle whose temperature is to be sensed.

A further object of this invention is to provide such anew and improvedswitch structure which is economical to produce and dependable inoperation.

Other objects will be in part obvious and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings, in which one of the various possibleembodiments of the invention is illustrated:

jFig. 1 is an elevational view in section of an electrical switchstructure embodying the invention, the switch being shown mounted on atube whose temperature is' to be sensed;

Fig. 2 is a sectional view taken along line 2-2 of Fig:1;-

Fig. 3 is a fragmentary elevational view on a slightly reduced scale ofthe cup-shaped member shown in Figs. 1 and 2;

Fig. 4 is a fragmentary plan view of the casing member as shown in Fig.3 along with a sectional fragment of the other casing member to showstructure of these parts by which they are mutually aligned;

Fig. 5 is a fragmentary view of the casing member as shown in Fig. 3 butrotated about its vertical axis;

Fig. 6 is a perspective view of the spring clip shown in Figs. 1 and 2;and

Fig. 7 is an enlarged fragmentary view illustrating the manner of and atool for applying the spring clip of Fig. 6 to mount the thermallyresponsive switch on a tube whose temperature is to be sensed.

Referring to Fig. 1, an electrical switch structure embodying theinvention is shown taking the form of a thermally responsive switchgenerally indicated by the reference numeral 10. Switch 10 includes afirst hollow, cup-shaped casing member 12 formed of one of the customarymoldable, electrically insulating, plastic materials and a secondhollow, cup-shaped casing member 14 formed of a suitable sheet materialhaving good thermal conductivity. The sheet material of which cup-shapedmember 14 is formed is preferably aluminum, copper, bronze or the likein that these materials are not only thermally conductive but readilylend themselves to the conventional drawing and forming operationsutilized to form'cup-shaped member 14 from fiat sheet stock. In theembodiment shown in the drawing, the sidewalls of casing members 12 and14 are cylindrical in form.

Hollow casing member 12 encloses an electrical contact arrangement ofany desired form which, in the embodiment shown in the drawing, includesa bridging contact member 16 disposed in operative relationship tospaced stationary contacts 18 and 20. According to the particularembodiment shown in the drawing, a compression spring 22 has one end inabutment with casing member 12 and its opposite end biased against aspringretaining member 24, the latter being engaged with bridgingcontact member 16 whereby spring 22 resiliently biases contact member 16from contacts-open position to the contacts-closed position shown inFig. 1. Each of stationary contacts 18 and 20 is carried by a terminal26 and 28, respectively, which extends through the casing to theexterior thereof.

Cup-shaped casing member 14 provides, adjacent its open end, twoannular, inwardly extending ledges or steps 30 and 32 about its innerperiphery, the step 30 nearer the open end of the cup-shaped memberextend-- ing outwardly of the other step 32.

Switch 10 includes a thermally responsive member 34 formed of composite,thermally responsive material. The thermally responsive material ofwhich element 34 is formed comprises at least two layers 36 and 38having mutually different coeflicients of thermal expansion and joinedtogether. Thermally responsive element 34 is provided with a deformationor dished shape capable of changing its shape suddenly with a snapmotion from the position shown in full lines in Figs. 1 and 2 to thebroken-line position shown in Fig. 1 when heated or cooled, as the casemay be, to a predetermined temperature. For certain applications, thematerial of layer 36 will have a greater coefficient of thermalexpansion than that of layer 38 whereby element 34 will snap from thefull-line (contacts-closed) position to the broken-line smallercoeificient of thermal expansion than that of layerv 38 whereby element34 will snap position to the contacts-open position upon cooling" fromthe contacts-closed (rather than heating, as before) of this element toa predetermined temperature. Element 34 resets itself by snapping backto the contacts-closed position upon cooling or heating to apredetermined temperature depending, of course, upon whether thiselement snaps to the contactsopen position upon heating or cooling,respectively; It will be apparent, however, that the invention is.applicable as well to other thermally responsive elements such, forexample, as those similar to element 34 but designed with a resettemperature above or below, as the case may be, the temperature range towhich the element Will be expected normally to encounter wherebyresetting thereof must be accomplished manually.

A motion transfer member 40 formed of electrical insulating material isprovided having one end bearing against thermally responsive element 34at substantially the central portion thereof and its other end adjacentand engageable with bridging contact member 16. It will be apparent,that, upon snapping of thermally responsive element 34 from thefull-line to the broken-line position shown in Fig. l, motion transfermember 46 will be moved upwardly as viewed in Figs. 1 and 2 againstbridging contact member 16 to move the latter against the bias of spring22 to contacts-open position. Upon snapping of thermally responsiveelement 34 fromj'the broken-line to the full-line position shown in Fig.1, the bridging contact member will be moved into contactsclosedposition with respect to stationary contacts 18 and 20 under theresilient bias exerted by spring 22.

According to the embodiment shown in the drawing, thermally responsiveelement is circular in shape. The outer, annular marginal periphery ofthermally responsive element 34 is engaged with and supported byinterionin wardly extending step 32, and the annular open end of casingmember 12 is in abutting engagement with internal, inwardly extendingstep 30. The open end of easing member 112 extends inwardly of step 30to overhang the latter at 42 whereby the outer margin of the thermallyresponsive element 34 is confined between step 32 on one side and theoverhanging portion 42 of casing member 12 on the other side. A slightclearance is provided between overhanging portion 42 of the open end ofeasing member 12 and the adjacent outer marginal portion of thethermally responsive element to permit unrestricted movement of thelatter between its two positions of stability as depicted in Fig. 1.Accordingly, a continuous, annular area of engagement between step 32and the thermally responsive element is effected by the constructionaccording'to the embodiment shown in the drawing.

Upon assembly of casing members 12 and 14 as shown in Fig. 1, cup-shapedmember 14 is inwardly deformed at 44 about its periphery to retain thecasing members in assembled relationship. Prior to assembly of thecasing members 12 and 14, casing member 14 is indented at 46 to providean inwardly extending projection 48 which interfits with acomplementary-shaped recess 50 provided by the adjacent outer surface ofeasing member 12 as shown in Figs. 2 and 4. In this manner, alignment ofcasing members 12 and 14 with each other during assembly is facilitatedand relative rotation thereafter between these casing members isprevented.

With casing members 12 and 14 assembled as shown in Fig. 1, a pair ofleads 45, 47 covered except at their end portions with electricalinsulation are inserted through respective apertures provided in thesidewall of easing member 14 (see the portion of aperture 49 for lead 45as shown in Fig. 1), and leads 45, 47 are welded to terminals 26 and 28,respectively. The interior of switch may be sealed from thecircumambient atmosphere by depositing a suitable sealing compound 51 tofill cupshaped member 14 between the internal surface thereof and theexternal, otherwise exposed surfaces of casing member 12, leads 45 and47 and the insulation within member 14 which covers these leads. Inaddition, a boot 52' formed of rubber or the like may be disposed aboutthat of surface 94 and between the latter recess and.

casing member 12 and adjacent the upper end of easing member 14 asviewed in Fig. 1, with sealing compound 54 disposed between the adjacentportions of the boot and casing member 14, all as shown in Fig. 7.Sealing compounds 51 and 54 may be any suitable, electricallyinsulating, thermosetting resin material which effectively bonds to thesurfaces contiguous therewith.

Cup-shaped member 14 is further provided with indentations 56 and 58 toprovide a pair of external shoulders 61 and 62, respectively, for thereception and retention of the inturned ends 64 and 66 of a U-shapedclip 68. U-shaped clip 68 is formed of relatively stiff, springymaterial such as 18-8 stainless steel.

The bottom of cup-shaped member 14 is provided with a recess 70conforming to the shape of an article such as a tube 72 whosetemperature is to be sensed by the thermally responsive element 34. Theyoke 74 of U shaped clip 68 is likewise provided with a depression orrecess/76 configured to conform to the shape of the article whosetemperature is to be sensed by the thermally responsive element. Each ofthe portions of U-shaped clip. 68 between recess'76 and the inturnedends 64 and 66 is provided with an aperture 78, 80, respectively, and asurface 82, 84, respectively, for the application of pressure toassemble the clip to cup-shaped member 14 with the article 72'therebetween. By virtue of apertures 78 and 86, a pair of outwardlyfacing abutments 79 and 81 are provided by the spring clip, each ofthese abutments lying between recess 76 and one of inturned ends 64 and66.

A description, now to follow, of the manner in which clip 68 is appliedto mount thermally responsive switch. 10 in good heat-conductivityrelation with article 72 will serve to indicate, in part, the improvedand advantageous characteristics of the invention. Referring to .Fig. 7,a tool generally indicated by the reference numeral 86 is providedcarrying a stud 88 grooved at 90. Tool 86 further includes a pressurefoot or pressure-applying surface 92. To mount cup-shaped member 14 ofswitch 10 tightly and securely on and against tube 72, cupshaped member14 is placed in assembled relationship with tube 72 as shown in Fig. 7whereby recess 70 of member 14 is engaged in interfitting relationshipwith the tube. One of the inturn'ed ends of U-shaped clip 68 (inturnedend 64 as shown in Fig. 7) is disposed in engagement with one ofexternal shoulders 60, 62 (shoulder 60 as shown in Fig. 7) as providedby cup-shaped member 14. The other inturned end 66 of clip 68 is' placedin engagement with a cam surface 94 provided by cup-shaped member 14between recess 72 and external shoulder 62. Tool 86 is juxtaposed withclip 68 as shown in Fig. 7 whereby abutment 79 provided by aperture 78is disposed in groove 90 of stud 88, and pressure foot 92 is inengagement with surface portion 84' of the clip. By swinging handle 96of the tool in a generally counterclockwise direction fromthe full-lineto the broken-line position shown in Fig. 7, it will be apparent that acombination of forces is applied to the spring clip including agenerally laterally directed force by stud 88fiand a generally upwardlydirected force ap plied by pressure foot 92. The combination of theseforces in concert with the action of end 66 of the spring. clip movingagainst cam surface 94 of the-cup-shaped member results in the stressingof the spring clip and movement thereof to the broken-line positionshown in. Fig. 7; this broken-line position corresponding to thefull-line position shown in Figs. 1 and 2.

A cam surface 98 is provided by cup-shaped member 14 which may beidentical to surface 94, but, as shown in the drawings, on the oppositeside of recess 70 from the remaining parts of switch 10 are firmlymounted;

' yoke 74 of the spring clip, respectively,

on article 72, and, due to the provision of recesses 70 and 76 in thebottom of cup-shaped member 14 and in rotation of cupshaped member 14relative to tube 72 is effectively resisted. .Also, it is to be notedthat the innermost edges of inturned ends 64 and 66 of the spring clipare concavely curved and that the indented portions of cupshaped member14 adjacent thereto are convexly curved whereby the latter respectivelyfit one within the curved portion of each of said inturned ends. Withthis construction, movement of the spring clip in the directions towardand away from the viewer as shown in Fig. 1 and relative to cup-shapedmember 14 is resisted.

It will be clear that with the construction as shown in Figs. 1 and 2,tube 72 is in good heat-transfer relation with cup-shaped member 14 forthe conduction of heat along acomparatively large area of mutual contacttherebetween. Also, a comparatively large area of mutual engagement isprovided between thermally responsive element 34 and cup-shaped member14 whereby a high degree of heat conductivity between these partsobtains. The result is that a good heat-transfer relationship existsbetween tube 72 and thermally responsive member 34 whereby changes inthe temperature of the tube, due, for example, to the flow ofrefrigerant therethrough (the starting and stopping of which flow may becontrolled by opening and closing of bridging contact member 16 withrespect to contacts 18 and 20) are quickly and effectively reflected bysnapping of the thermally responsive element between its respectivepositions of stability. The desirable result is achieved with theembodiment as shown in the drawings, that the flow of heat to and fromthe thermally responsive element is substantially uniform along theouter marginal portion of the latter toward and away from the centerthereof. It will be apparent that the invention permits sealing off thethermally responsive element from the circurnambient atmosphere whileproviding for the effective heat transfer characteristics describedabove. Furthermore, the manner of mounting the thermally responsiveswitch on the tube 72 according to the invention is greatly superior tothat, for example, of bolting-on from standpoints such as ease and costof mounting and minimal time required therefor. Along with theseadvantages, the cost of the parts of switches embodying the inventioncompares most favorably with those of prior constructions.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

Dimensions of certain of the parts as shown in the drawing have beenmodified for the purposes of clarity of illustration.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense.

We claim:

1. An electrical switch structure including a pair of electricalcontacts and a thermally responsive member, a hollow casing enclosingsaid contacts and said thermally responsive member, said thermallyresponsive member being operatively connected to open and close saidelectrical contacts, said casing including a member formed ofheat-conductive material, and said last-named member being configured toconform to the shape of an article whose temperature is to be sensed bysaid thermally responsive member means on said last-named member havingportions for releasably retaining a spring clip adapted to engageportions of an article whose temperature is to be sensed and retain saidswitch structure thereagainst.

2. An electrical switch structure comprising a hollow casing, a pair ofelectrical contacts and a thermally responsive element disposed withinsaid casing, said to open and close said contacts, said casing includinga cup-shaped member formed of heat-conductive ma-. terial, saidcup-shaped member being configured to com form to the shape of anarticle against which the cup-,

shaped member is to be mounted, means on said cup: shaped member forreleasably retaining a spring clip adapted to engage portions of saidarticle and retain said switch structure thereagainst.

3. A unitary cup-shaped member for mounting a thermally responsiveelement of an electrical switch in good heat transfer relation to anarticle whose temperature is to be sensed by the switch, a part of saidcup-shaped member providing inwardly extending shoulder means forsupporting the thermally responsive element within the cup-shapedmember, the external surface of said cup-shaped member being configuredat one portion thereof to conform to the shape of said article, and theexternal surface of said cup-shaped member having indented portions atopposite sides thereof for thereception of a clip to retain said articlefirmly against said one portion of the cup-shaped member.

4. An electrical switch structure comprising in combination: a hollowbase having an open end anden-- casing a pair of electrical contacts; athermally responsive element operatively connected for opening andclosing said contacts; a unitary cup-shaped member closing said open endof the base, said cup-shaped member being formed of heat-conductivesheet material and including, at opposite sides thereof, a firstlaterally extending por-;

tion providing an internal shoulder engaging said thermally responsiveelement and a second laterally extending portion providing an externalshoulder; and a portion ofv said cup-shaped member being configured toconform to the shape of an article whose temperature is to be sensed bythe thermally responsive element.

5. The electrical switch structure as set forth in claim I 4 including aU-shaped clip having inturned ends; each article whose temperature is tobe sensed by the thermally responsive element.

7. The electrical switch structure as set forth in claim 4 wherein saidinternal shoulder extends in engagement with the thermally responsiveelement throughout the inner periphery of said cup-shaped member.

8. A unitary cup-shaped member for closing an open end of an electricalswitch casing member, said cupshaped member being formed of a sheet ofheat-conductive material, the sidewall of said cup-shaped memberadjacent the open end thereof providing two inwardly extending shouldersabout its inner periphery, one of said shoulders being adapted to engagethe open end of said casing member and the other of said shoulders beingadapted to engage the outer marginal portion of a thermally responsiveelement, a portion of the cup-shaped member being recessed to conform tothe shape of an article against which the cup-shaped member is to bemounted, and the outer periphery of the sidewall of the cup-shapedmember being inwardly indented at opposite sides of the cup-shapedmember for the reception of a clip to retain said portion of thecup-shaped member firmly against said article.

9. In combination: a hollow switch casing member having an open end, apair of electrical contacts mounted within said casing member, acup-shaped member providing two inwardly extending steps about its innerperiphery, the one of said steps nearer the open end of the cup-shapedmember extending outwardly of the other step, the open end of saidcasing member lying against said one step and extending inwardly thereofto overhang the latter, a thermally responsive member having its outermarginal portion disposed between said other step and the overhangingportion of the end of said .casing member, said thermally responsivemember being operatively connected to open and close said con tacts inresponse to change in temperature of the thermally responsive member, aportion of said cup-shaped member being recessed to conform to the shapeof an article whose temperature is to be sensed by the thermallyresponsive member, said cup-shaped member being indented at oppositesides thereof, and a U-shaped spring clip for-straddling said article,said clip having inturned ends each of which is engaged with one of saidindents for firmly biasing said article against the recessed por-' tionof said portion of the cup in good heat-transfer relation through thecup-shaped member to said thermally responsive element.

10. In combination, a unitary cup-shaped member for mounting a thermallyresponsive element of an electrical switch in good heat transferrelation to an article whose temperature is to be controlled by theswitch, said cup-' shaped member including inwardly extending shouldermeans for mounting the thermally responsive element within thecup-shaped member and spaced indented portions, the external surface ofsaid cup-shaped member being configured at a portion thereof to conformto the shape of said article, a U-shaped spring clip having inturnedends received in said indented portions for retaining said articlefirmly against said portion of the cup-shaped member, and saidcup-shaped member providing a cam surface adjacent one of said indentedportions for camming one of the inturned endsof said spring clip intoreception with said one indented portion while the other end of saidspring clip is received in the other of said indented portions. 1

11. The combination as set forth in claim' 10 wherein said inturned endsof the U-shaped spring clip are concavely curved and the respectivesurfaces of said cupshaped member adjacent thereto are con'vexly' curvedand" fit one within the curved portion of each of said in turned ends.12. The combination as set forth in claim. 10. wherein ;said spring clipprovides an outwardly extending abutand the thermally responsiveelement; said casingincluding a cup-shaped member formed of heatconductive sheet material and providing an annular shoulder inengagement with the thermally responsive element along the outer marginof the latter; the bottom of the cupshaped member being recessed toconform to the shape of an article against which the cup-shaped memberis to be mounted, and the outer periphery ofthe sidewall of theycup-shaped member being inwardly indented at opposite sides of thecup-shaped member for the reception of a clip to retain said bottom ofthe cup-shaped member firmly against said article. I

References Cited in the file of this patent UNITED STATES PATENTSMoorhead -1 Feb. 18,

